CN201320745113.5 discloses a draining pump of the AC permanent magnet synchronous motor with an U-shaped iron core. However, during a test of the draining pump, since the iron core is not isolated from the rotor by a protective material, water entering the rotor cavity seeps into the iron core to lead its rusting, or water will seeps into the coil through the iron core to lead burning of the coil due to its short circuit. Moreover, water entering the rotor cavity will leaks outside the draining pump. Manufacturers suffer from the water leakage problem all the time.
In exiting technology, the AC permanent magnet synchronous motor has a structure of integrating the wound coil and the iron core with pump body by injection molding. Although it solves the technical problem of vibration noise during working of the draining pump, it does not solve the water leakage problem.
For example, an AC permanent magnet draining pump in current technology consists of an assembled coil and iron core, and a pump body formed by injection molding on the assembled coil and iron core and integrated with them. The pump body formed by injection molding has a rotor cavity for holding components of the rotor, and the polar arc part of the iron core and rotor barrel together form the rotor cavity. On the one hand, the pump body integrally formed by the injection molding avoids mutual movement of the iron core and the coil. On the other hand, since the internal surface of the rotor cavity is formed by the internal concave surface of the iron core and the rotor barrel together, and an air gap for the magnetic circuit between the permanent magnetic rotor and the iron core is very small, its electromagnetic efficiency is improved. However, it has the following disadvantages. After the draining pump works for a long time, a seal ring for preventing water from entering the rotor cavity wears out. In this case, water enters into the rotor cavity through the worn seal ring during working of the draining pump. After water enters the rotor cavity, it will seep into the iron core through the internal concave surface of the iron core exposing to the rotor cavity, which results in rust of the iron core. Along with rust increasing, the rotor may be jammed. In addition, if the plastic seal on rest surfaces except the internal concave surface of the iron core is poor, water entering the rotor cavity leaks through the space between laminations of the iron core, or the space between the iron core and the plastic, then leaks in the coil to lead to coil burning.
In order to avoid burnout of the coil or rusting of the iron core caused by the above-mentioned water leakage, a stainless steel barrel is provided in the rotor barrel in current technology to isolate the internal concave surface of the iron core from the permanent magnetic rotor. Although the stainless steel barrel prevents water entering the rotor cavity from contacting the iron core, its manufacturing process is complicated and its cost is high, and the electromagnetic efficiency is greatly reduced.